1. Field of the Invention
The present invention relates to a communication method associated with data transfer when directly connecting an information processing apparatus such as a computer and a peripheral device such as a digital camera or a printer via a communication line.
2. Description of the Related Art
Recently, since performance is improved and cost is decreasing in image input devices such as a digital camera and, and higher definition is achieved in recording devices such as a printer, a desire has been increasing for a direct printer capable of directly connecting the image input device and the recording device without passing through a host information processing apparatus such as a personal computer, and outputting images in the image input device.
A USB (Universal Serial Bus) interface, often adopted as means for connecting these devices, is an interface specification universal to various kinds of peripheral devices, which can connect a maximum of 127 devices in a daisy chain mode using the same connector. The USB further comprises a function called plug and play which allows connections of devices while a power source of the computer is turned on. The USB is constituted of a USB host and USB devices, and the USB devices include a USB function and a USB hub.
The USB function is a USB device capable of transmitting and receiving data and control information by way of a USB bus, and includes an input device such as a key board, an output device such a printer, and the like. The USB hub is a device for increasing connection points of the USB. The USB host exchanges information with the USB devices via a host controller, and manages the connected USB devices.
In order to perform printing from the PC via the USB, the PC and printer are connected as shown in FIG. 8. Further, a memory card compliant with PCMCIA such as a CompactFlash® card or smart media is often used as storage means for image data in the image input device such as a digital camera 803, and many of users who have a PC 802 connect the digital camera 803 to the PC 802 for the processing of the image data taken by the digital camera by means of photo retouching software or the like, thereby copying the image data stored in the memory card onto storage means such as a hard disk on the PC 802. Thus, the digital camera 803 is also connected to the PC 802, so that the connection of the devices will take a form of printer-PC-digital camera, as shown in FIG. 8.
However, since the digital camera 803 and printer 801 are both connected to the PC 802 and are not connected directly to each other, direct printing can not be performed from the digital camera 803 to the printer 801.
Furthermore, to enable the direct printing from the digital camera, a direct printer and the digital camera are directly connected via the USB. However, as the PC is not connected in this connection form, the data on the memory card of the digital camera can not be transferred to the PC.
Thus, in the connection form of printer-PC-digital camera, direct printing can not be performed from the digital camera to the printer, so that in the conventional connection form of direct printer-digital camera, the image data on the memory card of the digital camera can not be transferred directly to the storage means on the PC. Therefore, the connection of each device needs to be changed in each case, which causes trouble.
Especially in the USB, each network topology has one host, and the host device controls communication in the topology, but communication can not be performed between different network topologies.
Thus, when the PC, printer and digital camera are connected as above so that the printer functions as the host for the digital camera, two network topologies of PC-printer and printer-digital camera are formed, which does not allow the data transfer to the digital camera under the control of PC.